FIG. 1 shows an OLED device 100. The OLED device comprises a substrate 101, and one or more organic functional layers 102 formed between first and second electrodes 104 and 106. The electrodes can be patterned to form, for example, a plurality of OLED cells to create a pixelated OLED device. OLED cells are located in the device region where the cathodes and anodes overlap. Bond pads 110, which are coupled to the first and second electrodes, are provided to enable electrical connections to the OLED cells.
To protect the OLED cells from components of the environment such as moisture and/or air, a cap 112 encapsulates the device. The active materials of the OLED cells are sensitive and can be easily damaged due to mechanical contact with, for example, the cap. To prevent damage to the OLED cells, a cap or package is used. The cavity package provides a cavity 114 between the cap and OLED cells. The cavity also allows for the placement of desiccant materials to cope with finite leakage rate of the device.
The demand for thin and flexible devices requires the use of thinner components, such as the cap and the substrate. Decreasing the thickness of the cap reduces its mechanical stability, making it more prone to bending which can cause the cavity to collapse, thereby damaging the OLED cells. Spacer particles 116 are provided in the device region to prevent the cap from contacting the active components, thereby protecting them from damage.
However, the spherical shape of spacer particles exposes the edges of the electrode layer 106 in regions such as 118, to reaction with atmospheric components such as moisture and gases (e.g. oxygen). The penetration of atmospheric components into the interior of the OLED may result in the formation of impurities at the electrode-organic material interface. These impurities may cause separation of the electrode from the organic layer. Dark, non-emitting spots may appear at the areas of separation around the spacer particles due to the lack of current flow.
As evidenced from the foregoing discussion, it is therefore desirable to provide an OLED device having improved packaging, particularly those formed on thin or flexible substrates.